Carburetor



Oct. 26 1926. 1,604,279

w. L.. GUY

CARBURETOR 2 Sheets-Sheet i Filed Dec. 9, 1924 Oct. 26 1926. 1,604,279

W. GUY

CARBURETOR Filed Dec. 9, 1924 2 Sheets-Shed 2 INVENTOR.

A TTORNE Y.

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Patented Oct. 26, 1926.

Vi/ILLIAM LESLE GY, 0F BRliNCrI-IAM, ENGLAND, ASSIGNOR TO AMAC LIMITED,

QF BIRMNGHAM, ENG-LAND, A BRETISEI CGMPANY.

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Application filed December 9, 1924, Serial No, 754,825, and. in Great Britain December l5, 1923.

This invention relates to carburetors ot the kind embodying a plug throttle valve sliding across the air passage and two (or more) jet nozzles of which one is an idling or slow-running nozzle, the plug valve being generally bevelled upwards on the air inlet side, on which side the main jet of the two is placed.

lith this kind of carburetor there is generally either too rich or too weak a mixture at some point or points in the throttle curve, causing what are known as flat spots. It is the object of the present invention to provide a construction ot carburetor ot this kind in which this detect is minimized or eliminated.

According to this invention, the inlet ot the tube of the idling nozzle is connected by a passage with the outlet of the tube ot the next nozzle to come into operation.

The result is that at slow speeds air alone passes along the passage to the tube of the slow-running nozzle, but, as the throttle is opened and the draught of air over and through the slow-running tube increases, the air travelling along the passage takes up some fuel from the main iet nozzle which compensates for the tendency to become over-weak.

Preferably the passage is vented to the main air passage, this vent 'forming the normal outlet from the main jet tube, and with this vent may co-operate a sealing valve to enable a rich mixture to be obtained at starting. The scaling valve may also function to control the quality ot the mixture.

In the accompanying drawings,

Figure l is a vertical section showing one form ot carburetor' embodying this invention, with the throttle in position for starting and slow running.

Figure 2 is a similar view partly in elevation showing the throttle slightly raised.

Figures 3 and 4 are partial vertical sections showing the throttle and air control valves in other positions,

Figure 5 is a transverse section on the .line 5-5 of Figure 3, and

Figure 6 is a fragmentary sectional plan of Figure 5.

Like letters indicate like parts throughout the drawings.

ln this construction, there is a horizontal air passage A with a vertical tubular branch B in which slides a` plug throttle valve C which controls the travel of air along the horizontal passage. The bottom end of this plug valve is closed and is bevelled upwards at C2 towards the air intake A2.

ln the lower wall ot the air passage is an aperture which is iilled by means of a block D which carries the jet nozzles and tubes.

v The ioat chamber E is preferably iitted beneath the air passage and a screw E2 screwing into the block D may serve to hold the cup ot the float chamber in place against a circular flange E3 carried by the body of the air passage. j

rlChe air passage is preferably circular in cross section, but the block D is flat at the top, and this flat top lies slightly below the bottom ot the air passage A, so that there is a tlat surfaced recess A3 in the bottom of the air passage just beneath the plug valve C (see Figure 5). The lower end C3 of the plug valve C is adapted to enter this recess.

@n the side of the block D adjacent to the outlet end of the main air passage is a short vertical recess D2 through which passes small jet nozzle or other suitable fuel or fuel emulsion supplying device. rlChis is preferably a nozzle F dipping into the float chamber at F2. The recess D2 forms the slow-running tube, and, at a suitable level therein, which may be the bottom of it or thereabout, leads ott a small horizontal passage D3 leading firstly to a well DAI at or near the centre of the block, the well being in eiiect a vent to the small passage D3 leading into the main air passage.

From this well the passage D3 enlarges at D5 and leads olic to the side ot the block where it is open to the atmosphere. This part D5 oi' the passage 'forms a tube tor the main jet. G (dipping into the float chamber at G2), the tip of which enters the enlarged passage D5 instead of, as usual.J the main air passage, and its chie't communication with the main air passage is through the vent formed by the well Dt.

Assuming the plug throttle valve C to be in its lowest position, the recess A3 (Figure 5) just above the block D is cut ofi altogether and no fuel can be drawn out ot either jet nozzle. It the plug valve is raised slightly. as shown in Figure l, the recesses A3 will be shallow. Air is drawn up this recess and also over the top oi it. By selecting suitable proportions the right slowrunning mixture can be easily obtained.

Cit

It will be readily understood that as the plug throttle valve is raised this recess A3 increases in cross-sectional area very rapidly, more rapidly than does the area of the passage above the block and in the plane X X of the nozzle F. Thus, when the throttle valve is only a. little way open a state is reached when the cross-sectional area of the passage over the block tas obtained in the plane of the nozzle F at X X Figure 6) is equal to the cross-sectional area of the throte tle opening', and this position is hereinafter called the equal area position of the throttle valve. Figure 3 illustrates this.

As the throttle valve is opened up towards this equal area position the delivery from the idling nozzle F increases, but-.preferably just before the equal area position is reached the capacity of this nozzle is reached. Thus from this point up to the equal area position the mixture would tend to weaken, but this is counteracted by the increasing amount of air which passes along,r the passage D3 from the main jet nozzle tube D5 to the idling nozzle tube D2, taking` with it a certain amount of fuel from the main nozzle. The air passing` the main jet nozzle is then travelling only slowly, but it is sufficient to pick up some fuel from the main jet nozzle and carry it into the well and along' the small passage D3 to the idling` tube.

As the throttle is raised beyond the equal area position and inthe position as shown by Figure 8, suction becomes more and more heen over the mouth of the well Dt and gradually, as the throttle is raised, the suctionover the idling` nozzle F has less effect on the latter and becomes effective over the well D4. Thus fuel is drawn out of the main iet nozzle as well as a small amount from the idlingnozzle.

lt is owing to the interconnection. of the idliner and main tubes that the tendency to weakness of the mixture is prevented as the suction is being transferred from the idling jet to the main jet.

lf desired, there maybe a .sliding` valve H passing through the plug throttle valve C and adapted to close, or partially close, the month of the well D4. This valve may take the form of a. piece of rod of suitable dimensions controlled independently of the plug throttle valve. Its lower edge H2 is adapted either to seat in the mouth of the well or round the well as shown` so that, when starting up, suction along` the idling nozzle tube does not draw any uncarbureted air down the well, and therefore the mixture can then be slightly richer than usual. Varying,` the vertical position of this valve ll also varies the velocity of the air over the mouth of the well so that the valve functions also to control the mixture during normal running` when the suction is on the main jet nozzle only. Figure 4 illustrates the use of the valve H when the throttle C is half open, and the arrows in this and the other views show the variations in the direction of flow at the several throttle positions.

llftlternatively the foot of the valve does not completely seal the mouth of the well, and to prevent this the foot of the valve is niclted or roughened, as, for example, by forming` two or more diametrical cross cuts H3 (Figure Zl) in it, so that there is always a slight leak of air downwards into the well even though this mixture valve is shut.

By this means one of the great defects of carburetors of this type is overcome, and it is impossible to detect any sluggishness of the engine due to overriehness of the inisture or over weakness as the throttle is opened up slowly or closed slowly. This means that the well known flat spots"7 are lz'irgely eliminated.

that .l' claim as my invention and desirtl to secure by Letters Patent of the United States is 1. A carburetor of the type described including an idling)` nozzle and a main nozzle adapted to come into operation successively, a tube for each nozzle, and a passage connecting` the inlet of the tube of the idling nozzle with the outlet of the tube of the said main nozzle, a main air passage in the carburetor and a vent therefor in the passage connecting,` the said tubes.

2. A carburetor of the type described including an idling,r nozzle and a main nozzle adapted to come into operation successively and a tube for each nozzle and a passage connecting' the inlet of the tube of the idling nozzle with the outlet of the tube of the said main nozzle, and a main air passage in the carburetor and a vent therefor in the passano connecting` the said tubes and a sealing valve to control the outlet of said vent.

3. The device of claim Q said valve having' an edge provided with leakage passages.

ln testimony whereof l have signed my name to this slrecitication.

VILLIAM LESLH (l "it/Ff.

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